Isomerization of normal paraffins



Aug. 5, 1947. E. E. sENsEl.

ISOMERIZATIION OF NORMAL PARAFFINS Filed vJuly 21,

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Patented Aug. 5, 1947 ISOMERIZATION F NORMAL PARAFFNS Eugene E. Sensel, Beacon, N. Y., assigner to The Texas Company, New York, N. Y., a corporation of Delaware Application July 2.1, 1945, 'Serial No. 606,446

Claims. l

This invention relates to the catalytic conversion of hydrocarbons for the production of hydrocarbons suitable in the manufacture of gasoline. More particularly, the invention relates to the catalytic conversion of relatively low boiling saturated hydrocarbons to produce hydrocarbons of highly branched chain character.

The present application is a continuation in part of my pending application Serial No. 439,031, filed April 15, 1942. y

The invention contemplates subjecting feed hydrocarbons, such as saturated relatively low boiling hydrocarbons derived from a petroleum source, to the action of a conversion catalyst in a reaction Zone under conditions such that isomerization constitutes the principal reaction, and elfecting the reaction in the presence of a small amount of olenic hydrocarbon in such a way as to substantially promote the isomerization reaction.

More specifically the invention contemplates effecting the reaction so that a relatively small amount of low boiling olefin, in the presence 0f isoparaiiin hydrocarbon, is maintained in the isomerization reaction, the isoparain advantageously being present in substantial amount relative to the olefin at and subsequent to the initial contact between the feed hydrocarbon and the conversion catalyst. Advantageously both isoparaiiin and olefin are maintained present throughout the entire reaction.

It has been found that by carrying out the conversion in the foregoing manner and particularly at temperatures lower than normally used in isomerization, the hydrocarbon reaction product obtained contains a materially greater proportion of isomerized feed hydrocarbons than when the reaction is carried out in the substantial absence of olefin hydrocarbon. The reason for this is not clearly understood, but nevertheless the existence of a substantial promoting effect through having both olefin and isoparain present at least during the initial contact between feed hydrocarbon and catalyst appears to be substantiated by examples which will be described hereinafter.

In the isomerization of normal parafn hydrocarbons with a metallic halide catalyst it has been found desirableheretofore to remove olens from the feed to the reaction zone since under ordinary conditions olens, if present, appear to cause catalyst deterioration and result in a substantial decrease in the yield of isomerized hydrocarbons per unit of catalyst employed.

The present invention, however, involves having a substantial amount of isoparain present with the olen during the initial contact between the feed hydrocarbon and the catalyst and throughout substantially the entire reaction. Advantageously the isoparamn is present in substan- (Cl. i560-683.5)

tial molar excess over the olen` It appears that under these conditions the olefin is utilized in alkylating isoparafiins present in the reaction zone and is thereby consumed in the production of valuable hydrocarbon products rather than entering into reaction with the catalyst to form complex. At any rate under such conditions a definite promoting effect is realized.

The following experiments comprise batch liquid phase experiments in which normal butane was converted by the action of aluminum chloride and hydrogen halide at a temperature of about 150 F. In each experiment anhydrous aluminum chloride, hydrogen chloride and some hydrocarbon were charged to a reaction vessel provided with a stirrer and means for heating the vessel. The stirrer was then started and the temperature adjusted to the desired point, fol-- lowing which hydrocarbon feed was added slowly over a period of one hour, the mixture being stirred for 30 minutes after completion of the additionof the hydrocarbon. Thereafter, the reaction mixture Was drawn off and the hydrocarbon product separated into gaseous and liquid fractions respectively. The gaseous fraction comprised essentially isobutane, normal butane and lighter hydrocarbons, while the liquid fraction comprised normally liquid hydrocarbons free from butanes.

The following tabulation compares the amount of catalyst, hydrocarbon charge, and hydrocarbon product in parts by Weight. The composition of the gas and liquid fractions of the product is shown in per cent by weight.

A. B C

Catalyst:

Aluminum chloride 110 110 Hydrogen chloride 10 10 10 Reaction Temperature, F 1D0 100 150 Hydrocarbon Charge:

Normal butane 540 530 392 Isobutane 0 0 4l Ethylene 0 26 25 Mols of butane per mol of ethylene. 0 10.0 S. 3

Mols of isobutane per mol of ethylene. 0 0 0.8 Hydrocarbon Product: Gas fraction 530 500 404 Composition of Gas Fraction:

Per cent lighter than isobutane 0. 1 0. 5 l. 8

Per cent isobutane 11.0 19. 4 42.1

Per cent normal butane 87. 5 76. 0 n 5l. 9

Per cent isopentaue and heavier. l. 4 4. 1 4. 2 Yield of isobutane, per cent by weight basis normal butane charged 10. 2 18.0 32. 9

Liquid fraction None 40 58 Per cent yield of liquid fraction basis ethylene. 154 232 In experiment A the hydrocarbon charge consisted solely of normal butane.V In experiment B ethylene and normal ibutane was introduced continuously throughout the entire run. In experiment C isobutane was present initially in the reactor an'd ethyleneand'normal .butane introduced continuously throughout the entire run.

In experiment A it will be observed that under the conditions employed, the yield of isobutane amounted to 10.2% by weight of the normal butane charged. However, in experiment B with a small amount of ethylene present the yield of isobutane obtained amounted to 18.0% by weight of the normal butane charged. On the other hand, in experiment C Where a small amount of isobutane was initially present along with the ethylene the conversion of normal butane to isobutane was nearly doubled. The results in experiments B and C calculated on the basis of 100 pounds of normal butane charged may be tabulated as follows:

The liquid fractions obtained in experiments B and C comprised hydrocarbons boiling over the range about 85 to 175 F. and consisted mainly of pentanes and hexanes.

While normal butane was charged in the .foregoing experiments it is, of course, contemplated that the invention has application to the conversion of other paraffin hydrocanbons having from about 4 to about 11 carbon atoms per molecule and in particular hydrocarbons of about 4 to 6 carbon atoms as well as light naphtha fractions boiling in-the range up to about 150 to 170 F., for the purpose of converting normal and branched chain saturated hydrocarbons into branched and more highly branched chain saturated hydrocarbons. In addition it is contemplated that other types of hydrocarbons such as relatively low boiling naphthene hydrocarbons may be isomerized.

Other normally gaseous olens may Ibe employed besides ethylene, for example propylene, butylenes, amylenes; and mixtures thereof, al-4 though the lower molecular weight olefins are preferred. The proportion of olefin charged to the reaction may range from about 0.1 te 0.5% and advantageously not exceed about by volume on a liquid basis of the total hydrocarbon feed to the reaction. A fraction of one per cent has been found effective.

The isoparaffin introduced t0 the reaction advantageously comprises a relatively low boiling isoparafn such as isobutane or isopentane. It may be obtained from an extraneous source or may be separated from the reaction product and recycled to the reaction zone. The isoparaffin is added in the ratio of from about 1 to not more than 10 -mols of isoparaflin per mol 0f olen. As indicated in experiment C good results were obtained with a ratio of nearly 1. In no case, however, should the isoparaln in the feed exceed about 11% by volume of the normal paraffin undergoing conversion in the reaction zone.

'Ihe following results were obtained in a conf tinuous ow experiment in which normal butane was isomerized in the presence of small amounts of isopentane and isobutylene. In short, a stream of charge consisting of 88.49% normal butane 6.13% isopentane, 2.06% normal pentane, 2.11% isobutylene and 1.21% hydrogen chloride by weight, was continuously passed through a tower packed with 4 to 10 mesh anhydrous aluminum chloride, the catalyst mass being maintained at.

30 version catalyst.

a temperature of about 212 F. and under a pressure of about 175 pounds per square inch gauge. The eliiuent hydrocarbons were subjected to low temperature fractional distillation and were found to have the following composition in per cent .by volume:

Per cent Hydrocarbons of lofwer molecular weight than isobutane 1.0 Isobutane 67.5 Normal butane 26.9

Hydrocarbons having a molecular Weight greater lthan butane 15 Reference may lbe had to the accompanying drawing comprising a flow diagram illustrating one mode of practicing the invention in a con-` tinuous ow operation.

A hydrocarbon such as a normal paraiin hydrocarbon or mixture consisting essentially of normal paranin hydrocarbons is drawn from a source not shown through a pipe I and conducted to a heater 2 wherein it is heated to the reaction temperature. Oleiin may be present in the feed in the requisite amount or may be added separately through a pipe 5 and advantageously introduced to a fractionator 6. The hydrocarbons are advantageously scrubbed upon removal from the conversion unit to remove entrained catalyst and promoter.

The fractionator 6 may be operated so as to separate the hydrocarbon mixture into any desired number of fractions or may be operated so as to remove only gaseous constituents, the degasied hydrocarbons passing to a separate fractionator for further treatment. However, as indi-f` cated in the drawing the fractionator 6 may be operated so as to remove overhead a gas fraction through a pipe 'I and branch pipe 8.

Since this gaseous fraction removed through the pipe 'I may comprise substantial amounts of hydrogen chloride or other gaseous agents used in the reaction it is usually desirable to recycle the gaseous material to the conversion reaction. In such case the recycled material is returned through a pipe 9.

A side stream comprising isomerized hydrocarbons may be drawn olf through a pipe I0 and cooler II While a heavier fraction may be drawn off in liquid form from the bottom of the fractionator through a pipe I2.

If desired the liquid fraction drawn ol through the pipe I2 may be passed through a branch' pipe I3 for introduction to another fractionator I4 wherein the hydrocarbons are subjected to fur- 35 ther fractionation. In this instance an overhead fraction may be removed through a pipe I5 and a cooler I6 while a liquid fraction may be drawn oil' from the bottom of the fractionator through a pipe I'I.

Any portion, of either or both of the fractions removed through the coolers II and I6, may be recycled to the conversion unit.

For example, when charging a feed hydrocarbon consisting of normal butane the product fraction removed f rOm the cooler II may consist essentially ofisobutane, while the product', fraction removed from the cooler I6 may comprise essentially unreacted normal butane. The unreacted normal butane is advantageously recycled all or in part to the conversion unit together with a small amount of isobutane which may be obtained from the stream drawn off from the cooler Il. However, it is contemplated that the fractionation operations may be conducted so that the normal butane stream drawn off from the cooler I6 contains a small but sufficient amount of isoparafn to supply the isoparain required in the conversion unit.

.The recycled hydrocarbons may be returned through a pipe 20 communicating with the pipe 3 previously mentioned, or communicating by means of a branch pipe 2l with the pipe I previously mentioned.

Olefin hydrocarbon obtained from an extraneous source is conducted through a pipe 22 and advantageously commingled with the recycled hydrocarbons. On th'e other hand it may be injected directly with the feed hydrocarbon'or may be injected directly to the conversion unitv Whichever is desired. It may be injected in a stream which is rich in isoparaflin, or in a stream which is rich in normal paraffin.

Isoparamn from an extraneous source and which may be necessary in the early stages of the operation may be introduced through' a pipe 23.

Makeup catalyst and promoter may be passed to the conversion unit from a source not shown through a pipe 24.

The conversion unit may be of any conventional type depending upon the type of conversion operation employed. Thus, the catalyst may be employed in either solid or liquid form although the liquid form is usually preferred. In such case the catalyst may comprise a solid catalyst dissolved or suspended in a liquid carrier such as hydrocarbon or metallic halide-hydrocarbon complex. For example, an effective catalyst comv prises solid aluminum halide dissolved or suspended in aluminum halide-hydrocarbon complex.

The conversion unit may comprise a vessel containing a substantially stationary body of fluid catalyst through which the hydrocarbons undergoing treatment rise merely by difference in density. On the other hand, the reaction vessel may be of the agitated type, such agitation being imparted either by mech'anical stirring means or by rapid circulation of hydrocarbon or catalyst mixture through the reaction zone.

With the agitated type of apparatus it is usually desirable to provide adequate settling space or auxiliary settling chambers wherein separation between hydrocarbon `and catalyst phases occurs, the catalyst phase being returned all or in part to the reaction Zone, While the hydrocarbon phase is passed all or in part to the fractionating Zone or subsequent treating zone, that portion not so disposed of being returned to the reaction Zone.

The reaction may be carried out in the presence of extraneous agents such as hydrogen for the purpose of controlling or modifying the reaction.

Various metallic halide catalysts may be employed such as aluminum chloride, aluminum bromide, zirconium chloride, beryllium chloride, titanium tetrachloride, stannic tetrachloride, antimony chloride or mixtures of halides such as AlCla-sbCla, AlCla--NaCL etc,

p Suitable promoters other than hydrogen chloridemay be hydrogen bromide, hydrogen iodide, carbon tetrachloride, alkyl, aryl or acyl halides or any substance which is capable of liberating halogen halide after coming into contact with the metallic halide catalyst. Chlorine, bromine and iodine may be injected for purposes of promoting the. reaction, Alkyl halide formed by chlorinating a portion of the feed hydrocarbon to the reaction may be utilized as the promoter.

Other catalysts or promoters besides those speciiically mentioned above may be employed since it is contemplated that the process of this invention is applicable to the conversion of 4hydrocarbons by the action of any suitable catalyst wherein isomerization constitutes the principal reac-` tion.

WithV an aluminum halide-hydrogen Vhalide catalyst, such as aluminum chloride activated with hydrogen chloride, the temperature maintained in the reaction zone is preferably somewhat lower than that employed when effecting isomerization in the usual manner and in the absence of olen, However, temperatures may range from 75 F. to 200 or 250 F., the temperature selected depending on the particular stock,` promoter concentration and degree of conversion desired.

The feed hydrocarbon may be treated to remove objectionable compounds such as sulfur compounds and aromatic constituents, the presence of which is undesired when employing a catalyst such as aluminum halide.

The process of subjecting normal butane to catalytic conversion in liquid phase in the presence of aluminum halide catalyst and hydrogen halide promoter at temperatures of about F. with added olefin inan amount of about 0.5-10% by volume of the total hydrocarbon feed, together with added isobutane in an amount equivalent to 1-10 mols per mol of olefin but so that the isobutane does not exceed 50% by volume of the normal but-ane undergoing conversion in the reaction zone, to thereby effect isomerization of normal butane to isobutane as the prin-` cipal reaction, and the production of valuable normally liquid branched-chain paran hydrocarbons higher boiling than normal butane as a substantial but minor reaction, together with fractionation of the reaction products to separate isobutane as a principal product and the normally liquid hydrocarbons higher boiling than normal butane as a secondary product, and also separation of an intermediate fraction consisting mainly of normal butane with a minor proportion of isobutane for recycling to the conversion zone, is disclosed and claimed in the copending coi-owned application of Ernest F. Pevere, Serial No. 439,048, filed April l5, 1942.

Obviously many modifications and variations of the invention as above set forth may be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated by t'he apended claims.

I claim:

1. A continuous method of isomerizing saturated hydrocarbons which comprises passing a feed consisting essentially of normal parafn hydrocarbons to a reaction zone containing alumi num halide i-somerization catalyst in the presence of hydrogen halide and maintained at a temperature in the range about 75 to about 212 F., continuously adding to said stream prior to introduction to the reaction zone small but effective amounts of low boiling olen and isoparafn hydrocarbons, the amount of added olefin being Within the range of a fraction of 1% to 5% by volume on a liquid basis of the total feed to the reaction zone and the added isoparaflin being in a molar ratio of at least about 0.8 with respect to the olefin and not exceeding about 11% by volume of the normal parans undergoing conversion in the reaction zone, effecting isomerization of saturated feed hydrocarbons to a substantial extent as the principal reaction during passage of the hydrocarbons through the reaction zone, and continuously withdrawing hydrocarbon reaction products from the reaction zone, the proportions of added olefin and isoparain hydrocarbons being sulicient so that said products are substantially richer in isomerized feed hydrocarbons than when the reaction is effected under substantially similar conditions in the absence of the added olen and isoparaftin hydrocarbons.

2. A continuous method of isomerizing saturated hydrocarbons Which are substantially free from isoparafflns and olefns which comprises passing a stream consisting essentially of normal paraffin hydrocarbons having from about 4 to 6 carbon atoms per molecule to a reaction zone containing aluminum halide isomerization catalyst maintained in the presence of hydrogen halide at a temperature in the range about 75 to about 212 F., continuously adding to said stream prior to introduction to the reaction zone small but effective amounts of low boiling olefin and isoparaiiin hydrocarbons, added olefin amounting to a, fraction of 1% to 5% 'by volume on a liquid basis of the total hydrocarbon feed and the amount of added isoparain being at least the molar equivalent of the olen and not exceeding about 11% by volume of the normal paraiins undergoing conversion in the reaction zone, effecting isomerization of saturated feed hydrocarbons to a substantial extent and as the principal reaction during passage of the hydrocarbons through the reaction zone, and continuously withdrawing hydrocarbon reaction products from the reaction zone, the proportions of added olefin and isoparaiin hydrocarbons being suiicient so that said products are substantially richer in isomerized feed hydrocarbons than when the reaction is effected under substantially similar conditions in the absence of the added olefin and isoparaiin hydrocarbons.

3. The method according to claim 2 in which a vnormally gaseous olefin and an isoparaiin of about 4 to 5 carbon atoms per molecule are added to the saturated feed hydrocarbon stream prior to introduction to the reaction zone.

4. A continuous method for isomerizing normal butane which comprises continuously passing normal butane through a reaction zone containing a body of aluminum halide isomerization catalyst maintained under isomerizing conditions in the presence of hydrogen halide at a temperature in the range 75 F. and above, injecting small but effective amounts of a normally gaseous olefin and a low-boiling isoparaflin into the reaction zone in the region of initial Contact, between normal butane and the catalyst body, the injected normally gaseous olenn amounting to from a fraction of 1% to 5% by volume on a liquid basis of the total hydrocarbon feed to the reaction zone and the added low-boiling isoparaiiin being at least the molar equivalent of the ethylene and not exceeding about 11% by volume of the normal butane undergoing conversion in the reaction zone, effecting isomerization of normal butane to a Substantial extent as the principal reaction during passage of the normal butane through the reaction zone, and continuously withdrawing hydrocarbon reaction products from the reaction zone, the proportions of injected o1efin and isoparafiin being sufficient so that said products are substantially richer in isobutane than when the reactionis effected under substantially similar conditions in the absence of added olen and isoparafln.

5. The method of isomerizing normal butane which comprises continuously passing normal butane through a reaction zone containing a body of aluminum halide isomerization catalyst malntained under isomerizing conditions in the presence of hydrogen halide at a temperature in the range F. and above, injecting small but effective amounts of isobutylene and isopentane into the reaction zone in the region of initial contact between normal butane and the catalyst body, the amount of isobutylene so injected being in the range of a fraction of 1% to 5% by volume of the total hydrocarbon feed to the reaction zone and the amount of the injected isopentanc being at least the molar equivalent of the lsobutylene and not exceeding about 11% by volume of the normal butane undergoing conver sion in the reaction zone, effecting isomerization of normal butane to a substantial extent as the principal reaction during passage of the butane through the reaction zone, and continuously withdrawing hydrocarbon reaction products from the reaction zone, the proportions of injected isobutylene and isopentane being sufllcient so that said products are substantially richer in isobutane than when the reaction is effected under substantially similar conditions in the absence of the injected isobutylene and isopentane,

6. In the continuous isomerization of an isomerizable normal paraflin hydrocarbon with an aluminum halide isomerization catalyst the method of increasing the extent of conversion of the said normal parain to the corresponding lsoparaiin which comprises adding to a paran feed consisting essentially of a normal paraflin relatively small but; effective amounts of low boiling olefin and isoparan hydrocarbons, the oleiin amounting to from about a fraction of 1% to 5 volume per cent on a liquid basis of the total hydrocarbon feed and the lsoparaiin being at least about the molar equivalent of the olen and not exceeding about 11% by volume of the normal paraffin undergoing conversion, passing a stream of resulting mixture in contact with said catalyst in a reaction zone maintained under isomerizing conditions in the presence of a small amount of hydrogen halide at a temperature in the range 75 to at least about 212 F. such that isomerization of normal paraflin to the corresponding isoparaiiin constitutes the principal reaction, and discharging from said reaction zone after contact with the catalyst a hydrocarbon stream, the amount of added olefin and isoparafiin being sufficient so that said hydrocarbon stream is substantially richer in said isomerized hydrocarbon than when the reaction is eifected under substantially similar conditions in the absence of added olen and isoparafn.

7. The method according to claim 6 in which the normal paraflin consists essentially of normal butane.

8. The method according to claim 6 in which the aluminum halide is aluminum chloride.

9. A continuous method of isomerizing saturated feed hydrocarbons which are normally free from olens and isoparafiins which comprises maintaining a substantially stationary body of liquid aluminum halide isomerization catalyst in a reaction tower, maintaining said catalyst under isomerizing conditions in the presence of hydrogen halide at a temperature in the range about '75 to at least about 212 F., continuously passing to the lower portion of the reaction tower a stream of normal paran feed hydrocarbons, causing said feed hydrocarbons to rise through the catalyst body by difference in density, effecting initial contact between the saturated feed hydrocarbons and the catalyst body in the presence of small but effective amounts of added lowboiling olen and isoparafiln hydrocarbons, the olefins so added amounting to from a fraction of a per cent to not in excess of about 5% by Volume on a liquid basis of the total hydrocarbon feed to the reaction tower and the amount of added isoparaiiin being at least about the molar equivalent of the olefin and not exceeding about 11% by volume of the normal paraflins undergoing conversion in the reaction zoneJ effecting isomerization of saturated feed hydrocarbons to a substantial extent as the principal reaction during passage of the saturated hydrocarbons through the reaction zone, and continuously withdrawing hydrocarbon reaction products from the upper portion of the tower, the proportions of added olen and isoparain hydrocarbons being sufcient so that said products are substantially richer in isomerized hydrocarbons than when the reaction is effected in the absence of the added olen and isoparain hydrocarbons.

10. A continuous method of isomerizing normal butane to isobutane which comprises maintaining a body of aluminum chloride catalyst in a reaction zone, maintaining said catalyst under isomerizing conditions in the presence of a hydrogen halide at a temperature within the range of about 75 F. to at least about 212 F., preparing a normal butane feed to said reaction zone so that the normal butane contains small but controlled proportions of both a butylene and a lowboiling isoparaflin at the point of initial contact of the normal butane feed with said catalyst in the reaction zone, the butylene being in an amount from a fraction of 1% to not in excess of about 5% by volume of the total hydrocarbon feed to the reaction Zone and the isoparalin being at least about the molar equivalent of the butylene and not exceeding about 11% by volume of the normal butane undergoing conversion in said reaction Zone, passing said feed hydrocarbons through said reaction zone in contact with said catalyst so that isomerization of normal butane to isobutane occurs to a substantial extent and as the principal reaction of the process, and continuously withdrawing hydrocarbon reaction products from the reaction zone, the proportions of butylene and low-boiling isoparaiiin in the prepared feed being suiiicient so that said products are substantially richer in isobutane formed by isomerization of the normal butane than when said reaction is carried out under similar conditions in the absence of the butylene and isoparain.

EUGENE E. SENSEL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,266,012 DOuville et al. l. Dec. 16, 1941 2,265,870 Schuit Dec. 9, 1941 2,356,190 Voorhies, Jr Aug. 22, 1944 

